This invention relates to an endoscope system, and more particularly to an endoscope which is provided with means for adjusting a flow rate of a fluid supplied to a distal end of the endoscope or drawn off therefrom through its internal fluid passage.
Some endoscope systems comprise internal fluid passages for supplying or drawing off air and water and also a device for supplying or drawing off air and water through said fluid passages. With the above-mentioned type of endoscope system, it is preferred to adjust an amount of a fluid supplied or drawn off in accordance with the physiological condition of that portion of a coeliac cavity of, for example, a human body (hereinafter simply referred to as "the coeliac cavity") which is to be observed through the endoscope. A flow rate-adjusting device known to date is a mechanically adjustable valve. The conventional endoscope system comprises said mechanically adjustable valve which is provided in the control section of the endoscope to adjust a flow rate of a fluid running through the fluid passage. The control section provided with the mechanically adjustable valve undesirably has an increased weight and large size, giving rise to difficulties in operating and handling the control section. The control section of the prior art endoscope is provided with switches for actuating pumps for supplying and drawing off air and water, and enables an amount of a fluid conducted through any of the various fluid passages to be adjusted by intermittently actuating the selected one of the switches. However, a fluid flow rate-adjusting device proposed to date is still regarded as unadaptable for practical application, because a minute adjustment of a fluid flow rate is difficult, and the repeated operation of the switches involves complicated work.
It is accordingly an object of this invention to provide an endoscope system whose control section can minutely adjust a flow rate of a fluid running through the internal fluid passage, and is reduced in weight and size, thereby enabling the endoscope system to be easily operated.